A 14-year NASA mission has confirmed that a massive redistribution of freshwater is occurring across the Earth, with middle-latitude belts drying and the tropics and higher latitudes gaining water supplies.
The results, which are probably a combination of the effects of climate change, vast human withdrawals of groundwater and simple natural changes, could have profound consequences if they continue, pointing to a situation in which some highly populous regions could struggle to find enough water in the future.
"To me, the fact that we can see this very strong fingerprint of human activities on the global water redistribution, should be a cause for alarm," said Jay Famiglietti, a researcher at NASA's Jet Propulsion Laboratory and one of the authors of a new study published in Nature on Wednesday.
The results emerge from the 2002-2016 GRACE mission, which is short for Gravity Recovery and Climate Experiment, supplemented with other additional data sources. The GRACE mission, which recently ended but will soon be replaced by a "Follow-On" endeavor, consisted of two twin satellites in orbit that detected the tug of the Earth's gravity below them - and monitored mass changes based on slight differences in measurements by the two satellites.
Among all the very massive features on the Earth, water and ice are the ones that change most regularly. Thus, the GRACE data have been used to detect anything from the vast losses of ice in Greenland, Antarctica and Alaska, to changes in ocean currents, to the scale of the California drought.
The new research, led by NASA's Matthew Rodell, pulls together these and other findings to identify 34 global regions that either gained or lost more than 32 billion tons of water between 2002 and 2016. As the study notes, 32 billion tons is about the amount of water contained in Lake Mead. So all 34 areas saw very large changes.
The resulting map of the findings shows an overall pattern, in which ice sheets and glaciers lose by far the most mass at the poles, but at the same time, middle latitudes show multiple areas of growing dryness even as higher latitudes and the tropical belt tend to see increases in water.
Read more: NDTV